B. B. Doyle, W. Traub, G. P. Lorenzi
Jul 14, 1970
Citations
0
Influential Citations
48
Citations
Journal
Journal of molecular biology
Abstract
Abstract Poly( l -alanyl- l -alanyl-glycine) has been synthesized as a possible collagen model, and its conformation in solution and in the solid state has been studied. This polytripeptide was prepared by polymerizing the activated N-hydroxysuccinimide ester of the tripeptide unit. Circular dichroism spectra of this polymer in different solvents indicated that (1) no ordered structure was present in an ethylene glycol-water mixture at +24 °C or at − 112 °C; (2) some β structure, together with some random form was apparent in an ethylene glycol-hexafluoroisopropanol mixture; (3) in hexafluoroisopropanol there is evidence for another periodic structure, as yet undefined. X-ray diffraction patterns of (Ala-Ala-Gly)n recovered from water show it to have an antiparallel pleated-sheet conformation, but photographs of the polymer recovered from hexafluoroisopropanol solution indicate the occurrence of another structure, possibly α-helical. Infrared spectra of solutions, powders, and films of the polytripeptide are consistent with the circular dichroism and X-ray results. The dimensions of the (Ala-Ala-Gly)n pleated-sheet structure are similar to those of various silk fibroins and fibroin-like synthetic polypeptides, suggesting a similar arrangement of the chains, described in detail in this paper. The lack of any evidence for a collagen-like structure, either in the solid state or in solution, underlines the importance of proline and hydroxyproline residues in forming a triple-helical conformation.